Epidemiology of Japanese encephalitis in context with Indian scenario

Japanese encephalitis (JE) has been prevalent in various countries of East and South-East Asia since long. In India, JE virus activity was, however, first detected in 1952 through sero-epidemiological surveys in Nagpur district of Maharashtra and Chingleput district of Tamil Nadu. Japanese encephalitis as a disease was first reported in 1955 when cases of JE occurred in Vellore and Pondicherry in southern India. The virus was however, not recovered from man until 1958 when three isolations were made from the brain tissue of cases of encephalitis. This served to confirm JE as a case of encephalitis in India. Until early 1970s, the disease was reported only from southern India with periodic focal reports of its occurrence. A major outbreak resulting in 763 cases and 325 deaths [case-fatality rate (CFR)--42.6%] was reported from Bankura district of West Bengal in 1973. Subsequently, the disease spread to other states and caused a series of outbreaks in different parts of the country. In 1978, cases were reported from 21 states/UTs. Currently disease is reported from the states of Andhra Pradesh, Assam, Bihar, Goa, Haryana, Karnataka, Kerala, Mahrashtra, Manipur, Tamil Nadu, Uttar Pradesh, West Bengal and Nagaland. Till 2007 103389 AES/JE cases and 33729 deaths (CFR 32.62%) have been reported since 1978. Government of India launched vaccination campaign in highly endemic states of Assam, Karnataka, West Bengal and Uttar Pradesh in 2006 and in Andhra Pradesh, Bihar, Haryana, Maharashtra, Tamil Nadu in 2007 and 2008 respectively which has resulted in reduced incidence of JE in these states.